WASHINGTON — President-elect Joseph R. Biden Jr., racing against a surge in coronavirus cases and the emergence of a new variant that could significantly worsen the pandemic, is planning a vaccination offensive that calls for greatly expanding access to the vaccine while promising to use a wartime law to expand production.

But his plan is colliding with a sobering reality: With only two federally authorized vaccines, supplies will be scarce for the next several months, frustrating some state and local health officials who had hoped that the release of a federal stockpile of vaccine doses announced this week could alleviate that shortage. Trump administration officials clarified Friday that the existing stockpile would only go toward giving second doses to people who had already received the vaccine, and not to new groups of people.

“The vaccine rollout in the United States has been a dismal failure so far,” Mr. Biden said. “The honest truth is this, things will get worse before they get better. And the policy changes we are going to be making, they’re going to take time to show up in the Covid statistics.”

The president-elect said he would invoke the Defense Production Act, if necessary, to build up vaccine supply. But the team also sought to tamp down expectations. Mr. Biden said his plan “won’t mean that everyone in these groups will get vaccinated immediately, because supply is not where it needs to be.” But, he added, it will mean that as doses become available, “we’ll reach more people who need them.”
The New York Times